The body count left behind by an illness decimating bat colonies in the U.S. northeast continues to rise, sparking fears among wildlife officials it could spread along the critters' summer migration routes.

Experts on both sides of the border say Canada is well within reach of bats from infected populations.

The mysterious disease American biologists call white-nose syndrome tore through caves and mines this winter in several U.S. states, killing tens of thousands of bats.

White-nose syndrome drains the bats' fat reserves, often leaving behind skinny corpses with a flour-like dusting of fungus on the snout, wings or ears.

Biologists don't know how it is transmitted or if humans can contract the illness.

Alarmed by die-offs to their south, Quebec scientists combed four abandoned mines near the Vermont border in recent months. They did not find any traces of the disease.

But biologists say white-nose syndrome could spread to unaffected areas as bats embark on their summer travelling plans, which can take them hundreds of kilometres from their winter grottoes.

"That can spell real trouble if in fact that is how this affliction is spread," Scott Darling of the Vermont Fish and Wildlife Department told the Canadian Press.

Darling estimates as many as 500,000 bats in the United States could die from the disease, which has inflicted a 90 per cent mortality rate in some colonies.

"The size of this is likely to be overwhelming," he said. "Nobody has seen anything like this, that's the scary part."

Jacques Jutras, a biologist with Quebec's Wildlife Department, said he was relieved to hear the province's mines appeared to be clean after searches earlier this spring.

"We were nervous because we didn't know what might have happened here (in Quebec)," Jutras said.

Still, he remains concerned the infected American bats could still touch down in Quebec.

"Our bat populations are not so big," said Jutras, whose department will conduct additional mine checks later this year. "If this problem arrives in our colonies here it could be bad news."

Jutras said his department plans to send a representative to an international meeting on white-nose syndrome in Albany, N.Y., next month.

Meanwhile, signs of white-nose syndrome have popped up around Watertown, N.Y., some 50 kilometres from the Ontario border, but the province has yet to conduct any official quests for the disease.

"Ours is more of a passive monitoring and checking with other jurisdictions to see what's happening there and that sort of thing," said Jolanta Kowalski, spokeswoman for Ontario's Natural Resources Ministry.

A group of graduate biology students from the University of Western Ontario said they checked a mine near Fenelon Falls, Ont., in March, but found no signs of the sickness.

Scott Makepeace, a biologist with the New Brunswick Natural Resources Department, said there have been no bat surveys in the province, but the department is looking into it. "We're definitely concerned," Makepeace said.

"Some of our bats are probably the same bats that are wintering in New York, Vermont and New Hampshire."

Darling, meanwhile, said bat populations in the Elizabeth Mine, a grotto about 150 kilometres from the Quebec border, showed no symptoms of white-nose syndrome in February.

However, a follow-up search in early April uncovered all the signs of the illness, he said.

"In Vermont we've actually taken the position that we should consider all of our caves and mines as being affected by white-nose syndrome," he said in a telephone interview from Rutland, Vt.

Darling said Vermont's insectivorous bats should have enjoyed an unusually warm spring and bug-infested skies.

Instead, his department has received reports of dying bats flopping on driveways, others expiring in homes and even daytime sightings of the flying mammals.

"It's possible the bats lost so much fat in the caves and mines that even though they've made it through the winter they just can't seem to bounce back," he said.

White-nose syndrome was first documented in New York in the winter of 2006-07, but U.S. wildlife officials realized the depth of its impact only after a series of checks on hibernation caves that began earlier this winter.

Scientists have since found the sickness in Vermont, Massachusetts, Connecticut as well as suspected areas in Pennsylvania.